Magnetoresistive element and method of manufacturing the same

ABSTRACT

According to one embodiment, a magnetoresistive element is disclosed. The element includes a lower electrode, a stacked body provided on the lower electrode and including a first magnetic layer, a tunnel barrier layer and a second magnetic layer. The first magnetic layer is under the tunnel barrier layer, the second magnetic layer is on the tunnel barrier layer. The first magnetic layer includes a first region and a second region outside the first region to surround the first region. The second region includes an element in the first region and other element being different from the element.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/876,081, filed Sep. 10, 2013, the entire contents of which areincorporated herein by reference.

FIELD

Embodiments described herein relate generally to a magnetoresistiveelement and a method of manufacturing the same.

BACKGROUND

In recent years, a semiconductor memory utilizing a resistance variableelement as a memory element, such as a PRAM (phase-change random accessmemory) or an MRAM (magnetic random access memory), has been attractingattention and being developed. The MRAM is a device which performs amemory operation by storing “1” or “0” information in a memory cell byusing a magnetoresistive effect, and has features of nonvolatility,high-speed operation, high integration and high reliability.

One of magnetoresistive effect elements is a magnetic tunnel junction(MTJ) element including a three-layer multilayer structure of a storagelayer having a variable magnetization direction, an insulation film as atunnel barrier, and a reference layer which maintains a predeterminedmagnetization direction.

The resistance of the MTJ element varies depending on the magnetizationdirections of the storage layer and the reference layer, it takes aminimum value when the magnetization directions are parallel, and takesa maximum value when the magnetization directions are antiparallel, andinformation is stored by associating the parallel state and antiparallelstate with binary information “0” and binary information “1”,respectively.

The writing of information into the MTJ element involves amagnetic-field write scheme in which only the magnetization direction inthe storage layer is reversed by a current magnetic field that isgenerated when a current flowing is flowed through a write line, and awrite (spin injection write) scheme using spin angular momentum movementin which the magnetization direction in the storage layer is reversed bypassing a spin polarization current through the MTJ element itself.

In the former scheme, when the element size is reduced, the coercivityof a magnetic body constituting the storage layer increases and thewrite current tends to increase, and thus it is difficult to achieveboth the miniaturization and low electric current.

On the other hand, in the latter scheme (spin injection write scheme),spin polarized electron to be injected into the MTJ element decreaseswith the decrease of the volume of the magnetic layer constituting thestorage layer, so that it is expected that both the miniaturization andlow electric current may be easily achieved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view for explaining a manufacturing method of amagnetic memory according to a first embodiment.

FIG. 2 is a sectional view for explaining the manufacturing method ofthe magnetic memory according to the first embodiment following FIG. 1.

FIG. 3 is a sectional view for explaining the manufacturing method ofthe magnetic memory according to the first embodiment following FIG. 2.

FIG. 4 is a sectional view for explaining the manufacturing method ofthe magnetic memory according to the first embodiment following FIG. 3.

FIG. 5 is a sectional view for explaining the manufacturing methodaccording to the first embodiment following FIG. 4.

FIG. 6 is a sectional view for explaining the manufacturing methodaccording to the first embodiment following FIG. 5.

FIG. 7 is a sectional view indicating an MRAM according to a secondembodiment.

FIG. 8 is a sectional view for explaining a manufacturing method of amagnetic memory according to a third embodiment.

FIG. 9 is a sectional view for explaining the manufacturing method ofthe magnetic memory according to the third embodiment following FIG. 8.

DETAILED DESCRIPTION

Embodiments will be hereinafter described with reference to theaccompanying drawings. In the following drawings, portions correspondingto already-shown drawings will be denoted by the same signs (including asign having a different subscript), and their detailed explanations willbe omitted.

In general, according to one embodiment, a magnetoresistive element isdisclosed. The magnetoresistive element includes a lower electrode; astacked body provided on the lower electrode and including a firstmagnetic layer, a tunnel barrier layer and a second magnetic layer. Thefirst magnetic layer includes a first region and a second regionprovided outside the first region to surround the first region. Thesecond region includes an element included in the first region and otherelement being different from the element. A hard mask layer is providedon the stacked body. A cap layer is provided on the hard mask layer. Themagnetoresistive element further includes an upper electrode penetratingthe cap layer and contacting the hard mask.

According to an embodiment, a method for manufacturing amagnetoresistive element is disclosed. A stacked body is formed on asubstrate. The stacked body includes a first magnetic layer, a tunnelbarrier layer and a second magnetic layer. A hard mask layer is formedon the stacked body. A cap layer is formed on the hard mask layer. Thecap layer is processed. The stacked body and the hard mask are etchedusing the processed cap layer as a mask. Ions are implanted into aportion of the stacked body that is outside of the cap layer using thecap layer as a mask.

First Embodiment

FIGS. 1 to 6 are sectional views for explaining a method ofmanufacturing a magnetic memory according to a first embodiment. In thepresent embodiment, a case where the magnetic memory is a magneticrandom access memory (MRAM) will be described.

[FIG. 1]

A lower electrode 101, a storage layer 102, a tunnel barrier layer 103,a reference layer 104, a hard mask 105 having conductivity and a caplayer 106 having insulating properties are successively formed on asubstrate 100.

The substrate 100 comprises a silicon substrate (semiconductorsubstrate), a selection transistor formed on a surface of the siliconsubstrate and configured to select an MTJ element, an interlayerinsulating film, etc. The storage layer 102 comprises, for example,CoFeB. The tunnel barrier layer 103 comprises, for example, magnesiumoxide (MgO). The reference layer 102 comprises, for example, an alloy ofPt (precious metal) and Ni or Co (magnetic material). The hard mask 105comprises, for example, W, Ta or Ru. The cap layer 106 comprises, forexample, silicon nitride.

[FIG. 2]

The cap layer 106 is processed into a predetermined shape by etching thecap layer 106 using a resist pattern which is formed on the cap layer106 and not shown as a mask.

[FIG. 3]

The resist pattern and the cap layer 106 are used as a mask, and thehard mask 105 and the reference layer 104 are etched by RIE process. TheRIE process is performed under the condition that it stops on the tunnelbarrier layer 103. The resist pattern disappears during the RIE process,and then the cap layer 106 functions as a mask of the etching.

Damage is caused on the storage layer 102 outside the cap layer 106 bythe RIE process. The damage caused on the storage layer 102 maydeteriorate magnetic anisotropy, spin injection efficiency and an MRratio. Therefore, the damage may degrade the properties of the MTJelement.

It should be noted that the etching may be performed not only in RIEprocess but in IBE process.

[FIG. 4]

In the present embodiment, ions 107 are implanted into the storage layer102 using the cap layer 106 as a mask to reduce an influence of thedamage of the storage layer 102. In the figure, 102 a denotes a storagelayer of a portion into which the ions 107 are implanted (secondregion). The storage layer 102 a includes, for example, CoFeB (magneticmaterial) and the ions 107 (element). The storage layer 102 (firstregion) under the cap layer 106 does not include the ions 107 (element).

The ions 107 are implanted also into the tunnel barrier layer 103 andthe cap layer 106 on the storage layer 102 a. The ions 107 may beimplanted also into the lower electrode 101.

The thickness of the cap layer 106 is selected in such a manner that theions 107 are not to be implanted into the hard mask 105 when the ionsare implanted into the tunnel barrier layer 103 and the storage layer102 a. For example, the thickness of the cap layer 106 is greater thanthe sum of the thickness of the tunnel barrier layer 103 and thethickness of the storage layer 102 a. Thus, a problem that the ions 107are implanted into the hard mask 105 and resistance of the hard mask 105increases does not occur.

The reason why the influence of the damage of the storage layer 102 isreduced is that the storage layer 102 a is demagnetized by ionimplantation of the ions 107. By the implantation of the ions 107, thestorage layer 102 a is not only electrically deactivated, but it maybemagnetically deactivated.

An element used as the ions 107 is, for example, at least one of As, Ge,Ga, Sb, In, N, Ar, He, F, Cl, Br, I, O, Si, B, C, Zr, Tb and Ti. Amongthem, especially, As and Ge are effective in reducing the influence ofthe damage of the storage layer 102, since they have a large atomicradiuses. As and Ge may reduce a dose amount of the ion implantation.

[FIG. 5]

An insulating layer is formed on an entire surface to cover the stackedbody of the reference layer 104, the hard mask 105 and the cap layer106, thereafter, a sidewall 108 comprising the insulating layer isformed on the side wall of the stacked body of the reference layer 104,the hard mask 105 and the cap layer 106 by etching the entire surface ofthe insulating layer

[FIG. 6]

The tunnel barrier layer 103, the storage layer 102 a and the lowerelectrode 101 are processed by etching using the sidewall 108 as a mask.

An insulating layer 109 is formed on an entire surface to cover the caplayer 106 and the sidewall 108, thereafter, an opening reaching the hardmask 105 is formed in the insulating layer 109 and the cap layer 106,and the upper electrode 110 is formed in this opening.

Since the ions 107 are not implanted into the hard mask 105 in the stepof FIG. 4, increase of contact resistance between the hard mask 105 andthe upper electrode 110 is suppressed.

A process for forming the upper electrode 110 includes, for example,depositing conducting layer to be processed into the upper electrode 110to fill in the opening, and then planarizing surfaces of the conductinglayer and the insulating layer 109 by chemical mechanical polishing(CMP). As a result, the upper electrode 110 penetrating the cap layer106 and contacting the hard mask 105 is obtained.

Second Embodiment

FIG. 7 is a sectional view for explaining an MRAM according to a secondembodiment. The present embodiment is different from the firstembodiment in a positional relationship between a storage layer 102 anda reference layer 104, i.e., in that the storage layer 102 is arrangedhigher than the reference layer 104.

The MRAM according to the present embodiment can be obtained inaccordance with the manufacturing method according to the firstembodiment, and has an advantage similar to that of the firstembodiment. In FIG. 7, 104 a denotes a reference layer of a demagnetizedportion into which ions 107 are implanted (fourth region). The referencelayer 104 a includes a magnetic material and the ions 107 (element). Thereference layer 104 (third region) under a cap layer 106 does notinclude the ions 107 (element).

Third Embodiment

FIGS. 8 and 9 are sectional views for explaining a method ofmanufacturing an MRAM according to a third embodiment. In the presentembodiment, a cap layer 106 is not formed.

A step of FIG. 8 corresponds to the step of FIG. 4 in the firstembodiment (ion implantation).

In the present embodiment, the thickness of the hard mask 105 (D1) isset to be greater than the sum (D2) of the thickness of the tunnelbarrier layer 103 and the thickness of the storage layer 102 (D1>D2).

Thus, if ions 107 are implanted into the tunnel barrier layer 103 andthe storage layer 102 under the condition that the ions 107 are notimplanted into a lower electrode 101, a reference layer 104 is notdamaged by the ions 107, since the ions 107 implanted into the hard mask105 do not reach the reference layer 104.

Thereafter, the MRAM having a structure in which the upper electrode 110shown in FIG. 9 contacts the hard mask 105 is obtained through stepssimilar to the steps of FIGS. 5 and 6 in the first embodiment.

The manufacturing method according to the above-described embodimentsmay be applied also to the MTJ element including a shift cancellinglayer on the reference layer 104. Although MTJ elements having varioustypes of structures are present, the manufacturing methods according tothe embodiments may be applied generally to a method of manufacturing anMTJ element including implanting an element into a magnetic layer toreduce the influence of the damage of the magnetic layer caused by theRIE process.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel methods and systems describedherein may be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the methods andsystems described herein may be made without departing from the spiritof the inventions. The accompanying claims and their equivalents areintended to cover such forms or modifications as would fall within thescope and spirit of the inventions.

What is claimed is:
 1. A magnetoresistive element comprising: a lowerelectrode; and a stacked body provided on the lower electrode andcomprising a first magnetic layer, a tunnel barrier layer and a secondmagnetic layer, wherein the tunnel barrier layer is provided on thefirst magnetic layer, the second magnetic layer is provided on thetunnel barrier layer, the first magnetic layer comprises a first regionand a second region provided outside the first region to surround thefirst region, and the second region comprises an element included in thefirst region and other element being different from the element.
 2. Themagnetoresistive element according to claim 1, further comprising: ahard mask layer provided on the stacked body; a cap layer provided onthe hard mask layer; and an upper electrode penetrating the cap layerand contacting the hard mask.
 3. The magnetoresistive element accordingto claim 2, wherein the cap layer comprises the other element.
 4. Themagnetoresistive element according to claim 1, wherein the firstmagnetic layer is a storage layer, and the second region of the storagelayer is demagnetized.
 5. The magnetoresistive element according toclaim 1, wherein the first magnetic layer is a storage layer, the secondmagnetic layer is a reference layer, and widths of the storage layer andthe tunnel barrier layer are greater than a width of the referencelayer.
 6. The magnetoresistive element according to claim 1, wherein theother element is at least one of As, Ge, Ga, Sb, In, N, Ar, He, F, Cl,Br, I, O, Si, B, C, Zr, Tb and Ti.
 7. The magnetoresistive elementaccording to claim 1, wherein the first magnetic layer is a referencelayer, the second magnetic layer is a storage layer, the reference layercomprises the third region and a fourth region provided outside thethird region to surround the third region, and the fourth regioncomprises an element included in the third region and other elementbeing different from the element included in the third region.
 8. Themagnetoresistive element according to claim 2, wherein the cap layercomprises silicon nitride.
 9. A magnetoresistive element comprising: alower electrode; a stacked body provided on the lower electrode andcomprising a first magnetic layer, a tunnel barrier layer and a secondmagnetic layer; a hard mask layer provided on the stacked body, whereina thickness of the hard mask layer is greater than a sum of thethickness of the first magnetic layer and the thickness of the tunnelbarrier layer; and an upper electrode contacting the hard mask.
 10. Themagnetoresistive element according to claim 9, wherein the firstmagnetic layer comprises a first region and a second region providedoutside the first region to surround the first region, the second regioncomprises an element included in the first region and an element otherthan the element, the hard mask comprises the other element and thesecond magnetic layer fails to comprise the other element.
 11. Themagnetoresistive element according to claim 9, wherein the firstmagnetic layer is a storage layer, the second magnetic layer is areference layer.
 12. The magnetoresistive element according to claim 10,wherein the other element is at least one of As, Ge, Ga, Sb, In, N, Ar,He, F, Cl, Br, I, O, Si, B, C, Zr, Tb and Ti.
 13. The magnetoresistiveelement according to claim 9, wherein, the first magnetic layercomprises a third region and a fourth region provided outside the thirdregion to surround the third region, and wherein the fourth regioncomprises an element included in the third region and an element otherthan the element, the hard mask comprises the other element, and thesecond magnetic layer fails to comprise the other element.
 14. Themagnetoresistive element according to claim 9, wherein the firstmagnetic layer is a reference layer, the second magnetic layer is astorage layer.
 15. The magnetoresistive element according to claim 13,wherein the other element is least one of As, Ge, Ga, Sb, In, N, Ar, He,F, Cl, Br, I, O, Si, B, C, Zr, Tb and Ti.
 16. A method for manufacturinga magnetoresistive element comprising: forming a stacked body on asubstrate, the stacked body including a first magnetic layer, a tunnelbarrier layer and a second magnetic layer; forming a hard mask layer onthe stacked body; forming a cap layer on the hard mask layer; processingthe cap layer; etching the stacked body and the hard mask using theprocessed cap layer as a mask; and implanting ions into a portion of thestacked body that is outside of the cap layer using the cap layer as amask.
 17. The method according to claim 16, wherein the etching stops onthe tunnel barrier layer.
 18. The method according to claim 16, whereina thickness of the cap layer is greater than a sum of the thickness ofthe tunnel barrier layer and the thickness of the first magnetic layer.19. The method according to claim 16, wherein the ions are at least oneof As, Ge, Ga, Sb, In, N, Ar, He, F, Cl, Br, I, O, Si, B, C, Zr, Tb andTi.
 20. The method according to claim 16, further comprising forming anelectrode penetrating the cap layer and contacting the hard mask.